Assuming the question you really want answered is "what is the level of competition for jobs I am going to be up against", then the numbers of people attending FTO's is largely irrelevant. That is based on the argument that many many folk fall by the way side during the training. Bristol for example will send out thousands of sets of manuals but many will gather dust on peoples shelves and never get opened. Some people don't have the ability to pass the CPL or IR. Some brilliant aviators simply run out of money near the end and never finish.
Really what you need to get a feel for is the number of licence issues. The CAA website has various statistics going back a number of years. Its all there if you want to go and search under FCL and roam around a bit under the statistics header. Here is a link for the 2006-07 year to get you started.
http://www.caa.co.uk/docs/175/Licenc...20-%202007.pdf
You will never be able to nail down exactly the numbers of folks you will be competing with. The CAA data obviously only details UK issued licences and ratings. Some of those people will disappear back to their home countries seeking work. Others will come from the continent with non-CAA JAA licences. Perhaps it all balances out or maybe it doesn't. Who really knows.
At the end of the day its suffice to say that there will be hundreds if not thousands of people competing for a handful of jobs. The trick is to work out how to get to the front of the queue and get an interview in the first place. Flight training has never been cheaper (when compared to disposable income/average salaries etc) or more accessible which has increased the number of people undertaking the training and upped the ante.